Bird Diversity and Habitat Affinity on a Central Texas Ranch
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Bird diversity and abundance are indicators of the health of habitats. Due to declining numbers of avian species and an increased awareness of the importance and economic benefits of birds, new attention has been directed toward understanding birds. Knowledge of bird diversity, abundance, and utilization of habitats is imperative for maintaining and/or enhancing these species. The Point Count technique was used in 5 habitat types (Live Oak Woodland, Riparian Forest, Mesquite Savannah, Live Oak Savannah, and Juniper-Live Oak Woodland) representative of the Freeman Ranch, a heavily grazed ranch in Hays County, Texas. Baseline abundance and diversity data for birds were lacking for the ranch. A total of 600 Point Counts documented the presence of 8,381 individuals and 85 bird species on the ranch. In order to assess the vegetative composition in each of the 5 habitat types, the line intercept method and the vegetation profile board were used to calculate woody species composition and visual obstruction, respectively, in both horizontal and vertical strata of habitats. Avian and vegetative diversity in each habitat were determined by Brillouin's Index (H) of diversity. A 2-way ANOVA was calculated using H for bird diversity per habitat per season to determine how birds utilize each habitat throughout the year. A significant statistical difference was found in avian species both among seasons and among habitats. The Live Oak Woodland and the Riparian Forest habitats were most diverse areas overall for bird species due to a dense canopy and heterogeneous vegetative structure. Special attention was given to nonresident summer breeders and winter residents and neither showed a statistical difference in habitat utilization. However, in post hoc testing of winter resident diversity, the Riparian forest was more highly selected for by some bird species. Although the ranch rated "poor" in terms of vegetation due to the lack of climax species, the endangered Golden-checked Warbler was recorded in the Juniper-Live Oak Woodland, an otherwise low-rated habitat in terms of diversity. It is recommended that Point Count studies be repeated in future years to ascertain trends in avian populations, so that the avifauna of the ranch can be managed.
CitationBanks, B. W. (2000). Bird diversity and habitat affinity on a central Texas ranch (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.
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